1. Field of the Invention
The invention relates to a semiconductor device provided with a temperature detection circuit, particularly relates to a semiconductor device provided with a temperature detection function of a semiconductor chip on which a logical circuit such as a central processing unit (hereinafter referred to as CPU) is mounted.
2. Related Art
A demand for high speed in a CPU serving as a logical circuit has grown recently. In connection with such a demand, a high speed operation of the CPU causes the increase of heat generation, resulting in the occurrence of phenomenon of accelerating increase of resistance value, increase of power consumption and deterioration of a semiconductor device. As a result, there occur a disadvantage of the operation of the CPU and a problem of overdrive of the CPU and the like.
A countermeasure has been taken to avoid this problem such that a temperature sensor is disposed outside the CPU to monitor the temperature, thereby sending out a warning before the CPU is overdriven. There is a system, for example, as an example of such a countermeasure, having a configuration such that an interface circuit for connecting between the CPU and an external circuit is provided, and a temperature sensor for measuring an ambient temperature is disposed outside the CPU, and also a sensor control circuit for controlling the temperature sensor is provided while the sensor control circuit is connected to the interface circuit and the CPU.
According to the above conventional system, if an ambient temperature of the CPU is higher than a set value, the sensor control circuit once receives information and supplies a processed signal to the CPU, whereby a process is executed such that an operating frequency is reduced or a warning is sent out or the like, thereby preventing the CPU from being overdriven.
There is another prior art wherein a forward current is supplied from a constant current source by a PN junction diode, and voltages at both ends of the diode are measured at that time, thereby measuring a temperature utilizing a relation between the voltage and the temperature (see, e.g. JP-A 5-283749).
However, the method of disposing the temperature sensor outside the CPU merely detects the ambient temperature of the CPU but does not detect the temperature of the CPU per se, thereby arising a problem that the temperature of the chip has not been controlled in real time with good accuracy.